Recent advances in radio frequency microelectromechanical systems (RF MEMS) technologies have demonstrated on-chip integration of high-frequency signal processors alongside transistor circuits. In particular, aluminum nitride (AlN) based microresonators have been demonstrated with performance metrics which are readily applicable to modern wireless communication systems, i.e. low insertion loss, high f·Q product, and low motional impedance (sub 50Ω). In addition, the use of AlN in these microresonators allows these systems to be manufactured using micromachining technology, which may allow for features such as small form factor, CAD-definable frequency, and low cost due to batch-fabrication. These attributes make aluminum nitride-based micromechanical resonators a promising candidate for application in future generation wireless communication systems.
Despite all these advantages, however, there have been very few studies on the tuning methods of AlN resonators. The shortage of effective frequency tuning methods has limited the use of these resonators in timing applications where initial frequency accuracy is desirably tightly controlled. Deviation of the absolute frequencies of the fabricated resonators from the desired frequency is typical due to tolerances in the fabrication process. For example, an initial frequency variation of a few 1000s of ppm across a 6 inch wafer has been observed among AlN microresonators fabricated at Sandia National Laboratories. However, this is not a production process. Still it may be difficult to achieve 10s of ppm for the initial accuracy that is desired in timing applications, even with the rigor of production level process control. In addition, it is desirable for frequency shifts due to environment effects, such as temperature changes, to be compensated in high-precision applications.
Exemplary embodiments of the present invention may improve thyristor control in high current density applications, as well as applications in an ionizing radiation environment. These and other advantages of the present invention may be understood by those skilled in the art from the following detailed description.